Generally, a fuel cell includes a fuel cell stack 11 formed by a plurality of power generation cells 12 stacked as shown in FIG. 13. As illustrated in FIG. 14, an electrode assembly 15 is placed at a joint portion of a pair of frames 13, 14 forming the respective power generation cells 12. The electrode assembly 15 includes a solid electrolyte membrane 16, an electrode catalyst layer 17 positioned on the anode side, and an electrode catalyst layer 18 positioned on the cathode side. An outer peripheral edge of the solid electrolyte membrane 16 is fixed by being sandwiched by both of the frames 13, 14. An anode-side gas diffusion layer 19 is laminated on a surface of the electrode catalyst layer 17, and a cathode-side gas diffusion layer 20 is laminated on a surface of the electrode catalyst layer 18. In addition, an anode-side first gas passage forming member 21 is laminated on a surface of the gas diffusion layer 19, and a cathode-side second gas passage forming member 22 is laminated on a surface of the gas diffusion layer 20. A tabular separator 23 is bonded to a surface of the first gas passage forming member 21, and a tabular separator 24 is bonded to a surface of the second gas passage forming member 22.
As shown in FIGS. 14 and 15, the first gas passage forming member 21 includes a base plate portion 21a, which comes into contact with the separator 23, and a protrusion 21b formed integrally on a surface of the base plate portion 21a. A straight groove 21c, which forms a gas passage T, is formed between adjacent protrusions 21b as a result of being blocked by the surface of the gas diffusion layer 19. The second gas passage forming member 22 has the same configuration as the gas passage forming member 21. In other words, the second gas passage forming member 22 includes a base plate portion 22a, which comes into contact with the separator 24, and a protrusion 22b formed integrally on a surface of the base plate portion 22a. A straight groove 22c, which forms a passage F, is formed between the adjacent protrusions 22b as a result of being blocked by the surface of the gas diffusion layer 20. Fuel gas, or hydrogen gas, is supplied to the gas passage T from a fuel gas introducing passage Ml formed on the power generation cells 12, and oxidation gas is supplied to the passage F from an oxidation gas, or oxygen gas, introducing passage R1 (refer to FIG. 13) also formed on the power generation cells 12. As a result of supplying the fuel gas and the oxidation gas, the fuel gas and the oxidation gas electrochemically react in the electrode assembly 15 and thereby generate power. The fuel off-gas and the oxidation off-gas that have not been used in the power generation are respectively discharged outside the power generation cells 12 through a fuel off-gas discharging passage M2 and an oxidation off-gas discharging passage R2 (refer to FIG. 13) formed on the power generation cells 12 (refer to Patent Document 1).